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From: t901590@mp.cs.niu.edu (T.J. McNamee )
Newsgroups: comp.windows.ms
Subject: Re: Severe performance degradation with 386 enhanced mode, any tips?
Message-ID: <1991Feb4.185442.9185@mp.cs.niu.edu>
Date: 4 Feb 91 18:54:42 GMT
References: <1991Jan17.234310.6393@mintaka.lcs.mit.edu> <1991Jan20.183318.21088@vpnet.chi.il.us> <70249@microsoft.UUCP>
Organization: Northern Illinois University
Lines: 27

In article <70249@microsoft.UUCP> davidds@microsoft.UUCP (David D'SOUZA) writes:
>>In article <1991Jan17.234310.6393@mintaka.lcs.mit.edu> mikew@charm.LCS.MIT.EDU (Michael B. Williams) writes:
>>>A few of us out here are experiencing the same problem, but no one has
>>>yet suggested a solution that works.  My NEC Powermate 386SX gives the
>>>following SI times (values are approximate):
>>>
>>>Computing Index
>>>	From DOS (or Standard mode window): 15.2
>>>	From 386 mode: 4.6
>
>
>Windows Enhanced mode uses 32 bit code.   All memory accesses need to
>be 32 bits wide.  On 386 machines, motherboard memory fetches can be
>done 32 bits at a time.  Expansion memory is usually added to the
>mother board in which case you have 32 bit access to the new memory. 
>Some, such as Compaq, have a dedicated memory expansion slot which
>also allows memory to be fetched 32 bits at a time.
>   & then a bunch of stuff about 16-bit memory boards & acessing 16-bit
>   memory in 2 swipes, etc.

   As I understand it a 386DX has a 32-bit data bus, but the 386SX has
only a 16-bit data bus.  32-bit internally (registers & such) but
only a 16-bit interface to the outside world. (Much like the M68000)
Therefore ALL memory would be 16-bit and acessed in 2 swipes.
If I'm wrong, I'd like to know...I have a 386SX w/ win3.0

                                 Eric Moore